Highly-alkaline hair-relaxing or hair-straightening compositions are well known in the art and are commonly used in salons and in the home. These compositions usually have a highly-alkaline pH of above about 12 to about 14 due to the presence of an effective hair-relaxing or hair-straightening amount of water-soluble strongly alkaline material. Because of their causticity, highly-alkaline compositions, in some instances, alter the natural tone of human hair undesirably as discussed below. There is a desire and long-standing need to overcome this disadvantage during or before completing the hair-relaxing or hair-straightening process.
For convenience, the terms "hair-relaxing," "hair-texturizing," "hair-straightening" and grammatical variations thereof are used interchangeably herein to denote the chemical loosening or removal of some or substantially all of the naturally tight curl pattern from naturally curly or wavy hair at a pH above about 12. Generally, the term "permanent hair-straightening" denotes the removal of substantially all curliness to achieve a visibly straight configuration, whereas the terms "hair-relaxing" and "texturizing hair-straightening" each denotes varying degrees of loosened wave patterns. Most modern commercial products are commonly called hair relaxers, so this term will be used hereafter to encompass all of the foregoing products for ease and simplicity and not by way of limitation.
The term "tone" as used herein includes the natural color of the hair and those visually desirable characteristics normally associated therewith, such as highlights, brightness and shine or luster. For example, at high alkalinity the natural tone of dark brown hair is reddened, and the naturally "white" fibers of gray hair are undesirably and visibly yellowed and their normal highlighting brightness is correspondingly visibly dulled. Thus, the natural shine or luster of such alkali-treated hair, especially gray hair, is delustered and drabbed of its desirable highlights. The term "gray hair" denotes "head hair" which, en masse, is visibly subjectively classifiable as containing from about 1 percent to about 100 percent naturally "white" fibers; i.e., unpigmented. Thus, the term "gray hair," as used herein, encompasses albino hair, as well as hair commonly described as "salt and pepper" which has lost some or all of its natural pigmentation through normal aging.
Depending on the coarseness, degree of curliness, and resistance of the hair being relaxed, the user typically selects either a mild-strength, regular-strength or super-strength relaxer composition and varies the timing of the relaxing procedure by leaving the hair-relaxing composition in contact with the hair only long enough to remove the desired amount of curl. Consequently, the altered natural tone of alkali-relaxed hair becomes more noticeable and objectionable either as the alkaline strength of the composition increases, as the length of time increases in which the hair is in contact with the highly-alkaline relaxer composition, or when both conditions occur.
Naturally gray hair, in particular, when it is relaxed at high-alkalinity, develops, in some cases, an undesirable noticeable greenish yellow to yellowish brown tinge. This post-relaxer effect is commonly called "yellowing" or "discoloration." For convenience, the term "yellowing" and its grammatical variations will be used hereafter to denote any visibly altered tone of natural gray hair generally associated with the undesirable unnatural yellowish tinge caused by alkali-type hair relaxing. This type of yellowing is distinct from alterations in the tone of hair caused by environmental pollution, smoking, sun fading, and the like.
The mechanism of why the natural tone of the hair is altered by highly-alkaline hair-relaxing compositions is not understood but is generally attributed to the action of certain strong bases normally required for effective alkali-type hair-relaxing. The term "alkali-type hair-relaxing" as used herein refers to chemically relaxing hair at a highly-alkaline pH of above about 12, in which the sole hair-relaxing agent is a water-soluble strong chemical base. Naturally curly hair which has been subjected to alkali-type hair relaxing is generally referred to herein as "alkali-relaxed" hair. The term "naturally curly hair" denotes virgin hair having a tight curl or wave pattern and will be referred to herein generally as "hair", for convenience. At high alkalinity, strong chemical bases are known to convert the disulfide bonds of cystine in hair to stable, irreversible crosslinks of primarily lanthionine and some lysinoalanine. Thus, unlike thiol or bisulfite relaxers, a chemical oxidative or alkaline re-linking step is unnecessary.
Hence, the only step required following an alkali-type relaxing process is to promptly remove the hair relaxing composition by rinsing the hair with water, and substantially neutralize all excess alkaline material remaining to avoid and minimize damage to the hair protein or skin. For this purpose, a non-alkaline base-neutralizing shampoo is commonly used to neutralize and remove excess residual alkaline material from the hair and scalp. The terms "neutralizer" and "neutralizer shampoo," therefore, are used herein to generally denote a post-relaxer composition capable of accomplishing the foregoing neutralization of residual alkalinity when it is applied substantially immediately following the removal of hair-relaxing composition from the hair.
The term "strong base" as used herein denotes cosmetically useful water-soluble, non-volatile inorganic caustic bases and relatively strong organic bases capable of relaxing the hair. For example, alkali metal hydroxide, such as sodium hydroxide (lye), potassium hydroxide, or lithium hydroxide; alkali earth metal hydroxide, such as calcium hydroxide, barium hydroxide and strontium hydroxide or oxides thereof capable of forming hydroxides in water; or a relatively strong organic base, such as guanidine, guanidine hydroxide or quaternary ammonium hydroxide is usually used.
Modern highly-alkaline hair relaxers are commonly called "no-base" hair relaxers and are referred to as "lye," "non-lye" and "no-lye" hair relaxers as discussed below. The term "no-base" in referring to hair relaxers means that the scalp need not be coated with a skin-protective oleaginous base, such as petrolatum, mineral oil and lanolin, before applying a highly-alkaline hair relaxer. The term "no-base hair relaxer," therefore, as used herein generally encompasses a highly-alkaline hair-relaxing product in which some of the skin protective oleaginous material is emulsified in an aqueous composition, preferably in the form of a viscous cream, and does not require the use of a skin-protective base. No-base hair relaxers are commercially supplied as either a "single product" kit or a "two-part product" kit.
In commercial practice, a single product relaxer kit generally denotes a no-base hair relaxer formulation which usually contains, as the sole active hair-relaxing agent, an alkali metal hydroxide. When the alkali metal hydroxide is a caustic base such as sodium hydroxide or potassium hydroxide, the composition is generally referred to as a "lye-type" hair relaxer. When the active hair-relaxing agent is lithium hydroxide or a salt of a strong base, such as sodium carbonate, the composition is referred to herein as a "non-lye" hair relaxer. The product is generally applied in the form of a viscous emulsion cream directly from its container to the hair for use.
A particularly popular type of no-base formulation is commonly called a "no-lye" hair relaxer. The term "no-lye" means that the active hair-relaxing agent is an organic chemical base instead of inorganic caustic base (lye). In commercial practice, the relatively strong organic chemical base, guanidine is usually present in the form of guanidine hydroxide in a no-lye hair relaxer. Guanidine hydroxide, however, is not generally stable for long periods in aqueous solutions, so it must be prepared fresh just before using.
Consequently, no-base, no-lye type hair relaxers are usually supplied commercially as a two-part product relaxer kit in which the guanidine hydroxide is generally prepared in situ from guanidine carbonate and calcium hydroxide. Hence, one part of the product contains the guanidine carbonate packaged in substantially liquid aqueous form, commonly called the "activator." The other part of the product is a package containing relatively high amounts of about 4 percent to about 7 percent calcium hydroxide emulsified in the form of a viscous cream. Prior to using, the consumer or beautician mixes the cream and activator portions of the kit together. The resulting no-base, no-lye hair relaxer cream is then applied to the hair relatively promptly (preferably within several hours and less than 24 hours). For convenience, the term no-lye hair relaxer, therefore, refers to the foregoing admixture.
The yellowing of the tone of naturally gray relaxed hair is more pronounced after a no-base, no-lye hair relaxer is used than when a lye-type hair relaxer is used. A yellow tinge on gray hair is particularly undesirable, because the white fibers in gray hair normally have a desirable natural bright tone which gives the hair highlights, whereas when yellowed, the hair looks dull, drab and lackluster.
Even though some or most of the visible yellowing caused by alkali-type hair relaxing sometimes gradually fades over a period of days, most persons generally find this yellowing highly objectionable. Consequently, the majority of consumers resort to some remedial masking of any persistent post-relaxer yellowish tinge by applying a temporary or semipermanent hair coloring, usually a violet or silver rinse. However, such colorant rinses can produce further unnatural or unsatisfactory tones, such as greens and blues.
Some success in removing visible yellowish tinges which persist in the interim between relaxer treatments has been achieved with an oily color corrective product known in the professional salon arts when it is mixed with a relatively high concentration of hydrogen peroxide of above about 5 percent. However, this practice is unsatisfactory, because at concentrations above about 3 percent, hydrogen peroxide can irritate or burn the scalp or skin, bleach the natural underlying color of the hair and increase the risk of chemical damage to the virgin outgrowth portion of the hair on later receiving a hair relaxer treatment.
Some strides have been made in formulating lye-type hair relaxer compositions that are substantially non-yellowing to gray hair during the hair relaxing step by including hair keratin-disulfide reducing agents having functional sulfhydydrol groups, such as dimercaptoadipic acid or cysteine, as ingredients of the alkaline relaxer cream. See U.S. Pat. Nos. 4,898,726 and 4,992,267, respectively, which issued to the present assignee and the disclosures of which are incorporated herein by reference. However, the vast majority of popular hair relaxers otherwise formulated and presently sold do not contain the foregoing beneficial ingredients.
Therefore, the need to overcome tonal alteration problems before the alkali relaxing process is completed when conventional no-base hair relaxer systems are used still exists, particularly during the use of no-base, no-lye hair relaxer systems.
An ideal solution is to provide a relatively simple hair relaxer system and method for enhancing and restoring a natural tone to alkali-relaxed hair, especially to alkali-relaxed gray hair, in a post-relaxing step performed prior to completing a hair relaxing treatment. The hair relaxer and post-relaxer hair brightener system and method of this invention provides such a solution to this long-standing need.